DK2870108T3

DK2870108T3 - Plant and process for working up bottom water and sludge

Info

Publication number: DK2870108T3
Application number: DK13732932.2T
Authority: DK
Inventors: Klaus-Rainer Witte
Original assignee: Gea Mechanical Equipment Gmbh
Priority date: 2012-07-05
Filing date: 2013-07-01
Publication date: 2018-07-30
Also published as: PL2870108T3; JP6265981B2; KR20150034763A; EP2870108B1; EP2870108A1; CN104487389A; SG11201500049TA; KR102134047B1; WO2014005967A1; TR201809465T4; JP2015527185A; DE102012106019A1; HRP20180990T1

Abstract

The invention relates to a system and a method for cleaning bilge water, wherein the system has at least the following features: a bilge water tank (1) for bilge water, a centrifuge (6) for separating an oil phase (O) and a solid-like sludge phase (S2) from the bilge water to be cleaned, and a sludge collection tank (10) for collecting the separated oil phase (O) and the sludge phase (S2), wherein the sludge collection tank (10) has a return line (L12), which opens into a line (L1) that is arranged between the bilge water tank (1) for bilge water and the centrifuge (6).

Description

The present invention relates to a system and a method for reprocessing bilge water.

Bilge water occurs during operation on ships, but, because of statutory regulations, should not be discharged, unpurified, into the ocean. It is therefore expedient to reprocess or purify the bilge water directly onboard ships to an extent such that it can be discharged directly into the ocean after purification. For this purpose, sediments in the form of a sludge phase and oil residues in the form of an oil phase are separated out of the bilge water and, as a rule, are stored in a common sludge collection tank, together with sludge residues from other processes, for example until the ship reaches port.

From WO 00/29334 A1 a plant for cleaning bilge water is known, comprising the following: a bilge water tank for bilge water, a reactor tank for heating the bilge water, a station for adding chemicals after the tank, a centrifuge for separating the oil phase and a solid-like sludge phase from the bilge water to be cleaned, a sludge collection tank for collecting the separated sludge phase and an oil collection tank for collecting the separated oil phase, wherein recirculation lines extend from the sludge collection tank and the oil collection tank into the reactor tank.

Since the capacity of the sludge collection tank is often limited, it is expedient to reduce further the quantity of liquid to be stored in the sludge collection tank.

The object of the invention is to solve this problem.

The invention achieves this object by means of a system having the features of claim 1 and a method having the features of claim 11.

By products collected in the sludge collection tank, in this case, in particular, an aqueous sludge phase which has settled in the sludge collection tank, being recirculated into the centrifuge, a second centrifugal reprocessing/purification of the recirculated part of the solid or sludge phase can take place, as a result of which, overall, the quantity of dischargeable water can be increased or the quantity of sludge phase can be further reduced, so that there is a longer period of time until the sludge collection tank reaches its maximum filling level. What is more, compared to WO 00/29334 A1, less tanks are needed.

Advantageous refinements are the subject matter of the subclaims.

Preferably, a nonreturn valve is connected, downstream of the sludge collection tank, into the recirculation line, in order to prevent a backflow of sludge into this collection tank.

Furthermore, a pump, preferably a regulated sludge pump, which allows a metered recirculation/return of the sludge phase, may be arranged in the recirculation line.

In this case, it is preferable, further, if a bilge water pump P1 is arranged in the line L1 downstream of the nonreturn valve and downstream of the issue of the recirculation line into the line.

Preferably, the power of the bilge water pump is higher is than that of the sludge pump.

In order to utilize optimally the power of the bilge water pump, it is advantageous if the line into which the recirculation line for the sludge phase issues is arranged between the bilge water tank for bilge water and the bilge water pump.

Preferably, the power of the bilge water pump is always higher than the power of the sludge pump, so that further transport in the direction of the centrifuge takes place. In this case, a nonreturn valve arranged downstream of the bilge water tank preferably and advantageously prevents further transport of the sludge into the bilge water tank for bilge water, in the event that the bilge water pump fails.

Since it is primarily expedient to reprocess once more essentially only the sludge phase, but not also part of the separated oil phase, it is advantageous if recirculation is arranged in the bottom and/or on a wall in the lower third of the sludge collection tank. The sludge collection tank in this case acts as a kind of settling tank, in which the heavier aqueous sludge phase collects in the lower region of the tank and in which the oil phase floats on top.

The oil content of the bilge water before its clarification will preferably amount to less than 25% by volume, and therefore, when sludge is being metered into bilge water, care must be taken to ensure that sludge recirculation is stopped beyond a specific oil content, until more sludge with higher water fractions has settled again in the sludge collection tank. The oil content may be monitored directly by a checking device in the recirculation or in the line to the centrifuge or indirectly by a flowmeter in the water drain of the centrifuge.

In order additionally to increase the efficiency of the method, before the centrifugal purification/-reprocessing of the bilge water one or both of the following steps may be carried out: filtration and/or heating of the bilge water.

The recirculation of the sludge phase preferably takes place before the centrifuge carries out any emptying.

Since the sludge phase mostly has only a low oil content, it can be processed separately, so that less filling mass is delivered to the sludge collection tank. It is therefore advantageous if the sludge is upgraded in a tank separated spatially from the sludge collection tank.

This upgrading may take place by heating, filtration or by separation in a sludge dewatering device (“sludge concentration unit”).

The invention is described in more detail, with reference to exemplary embodiments, by means of the following figures in which: fig. 1 shows a system according to the invention for reprocessing bilge water; fig. 2 shows an already known system for reprocessing bilge water; and fig. 3 shows a further variant of the system according to the invention.

Fig. 2 shows a known system for reprocessing bilge water which will be described first.

Bilge water usually collects/forms in the engine room of a ship. It may be formed, for example, from seawater and cooling water leakages, condensation water or cleaning water and contains the actual water as the main constituent and, as a rule, further constituents, such as residues of fuel, of lubricating oil or of other oils.

The problem with this is that the bilge water should not be returned, untreated or simply diluted, to the ocean. Thus, an oil content of less than 15 ppm (IMO regulations) is deemed to be a limit value for the introduction of bilge water into the ocean outside what are known as the 12 mile zones. In special protected areas, the permitted oil content sometimes even lies at a maximum of 5 ppm. The presence of a licenced and fully functioning bilge water deoiler onboard ships is therefore prescribed by law.

These limit values can be adhered to by means of the patented device and the method.

In the known system, depicted in fig. 2, for the purification of bilge water B, the bilge water from the ship introduced into a bilge water tank 1 and preferably collected there.

The bilge water is first conducted from the bilge water tank 1 by a line L1 by means of a bilge water pump P1 through a filter system 2, in order to remove solid particles S1 from the water.

The water emerging from the filter system is led further on by a line L2, preferably through a heating device, such as a steam heater 4, which has a steam inflow 3 for the introduction of hot steam and a condensate outflow 5 for the discharge of hot condensate.

The heated/warmed bilge water, which can consequently be purified more effectively, in particular, in terms of the oil constituents, flows out of the heating device through a line L3 and a changeover valve V1 into a centrifuge 6, preferably a separator, in particular a three-phase separator, where separation of the bilge water into a water phase W, an oil phase O and a sludge phase S takes place in the centrifugal field.

The centrifuge 6 is assigned a process water line L4 for the addition of control water L6 and filling and displacement water L5 which can be introduced via the valve V6 into the closing chamber of the separator drum or via the valve V5 into the supply line L6 to the centrifuge 6.

The purified bilge water W is discharged out of the centrifuge through a line L7 which is bypassed (valve V3) by an oil monitor 13, in order to monitor it continu ously for its residual oil content. The changeover valve V4 is controlled by the oil monitor.

If the oil content lies below a desired value of preferably 15 ppm or, optionally, 5 ppm, disposal of the clarified bilge water into the ocean through a drainage line L8 can take place. If, by contrast, the oil content lies above a stipulated desired value, the bilge water is not sufficiently clarified and is returned to the bilge water collection tank 1 via a recirculation line L10.

The sludge phase S2 expelled from the centrifuge 6 into a solids trap 7 is collected in an intermediate container 9 and conducted by means of a pump P2 through the line L9 into a sludge collection tank 10.

The oil phase O discharged from the centrifuge 6 is discharged from the latter through a line L11 which preferably issues into the line L9 for introducing the sludge phase into the sludge collection tank 10 or directly into the sludge collection tank 10.

Overall, the method of fig. 2 affords the particular advantage that the main constituent of the bilge water, that is to say the water contained in it, can, as a rule, be conducted directly into the ocean after clarification, so that already a relatively low storage capacity is required for collecting and storing the bilge water.

This system and a correspondingly accompanying method have therefore basically proved to be successful, but, according to the invention, are developed substantially even further.

Fig. 1 shows a system according to the invention which has a set-up similar to that of fig. 2.

Flowever, in addition to the components of figure 1, the system also has the following feature: a recirculation line L12, by means of which liquid, in particular a still free-flowing aqueous sludge phase, can be recirculated out of the sludge collection tank 10 into a line, connected between the bilge water collection tank 1 and the pump P1, and into the centrifuge 6.

This recirculation is especially advantageous for the following reasons.

The sludge collection tank 10 acts as a kind of settling tank, in which the (still water-containing) sludge phase S2 gradually settles, while the oil-containing phase O floats on the sludge phase S2. Via the settled sludge phase S2 being recirculated out of the sludge collection tank 10 through the recirculation line L12, the level in the sludge collection tank 10 is lowered, so that it can accommodate a larger volume of sludge and oil.

Preferably and especially advantageously, the recirculation line L12 issues from the sludge collection tank 10 into the (suction) line L1 between the sludge collection tank 10 and the bilge water inflow pump P1.

Preferably, a nonreturn valve (not shown) is arranged in the line L1, so that no backflow of the aqueous sludge phase S2 out of the sludge collection tank 10 into the comparatively cleaner bilge water of the bilge water tank 1 can take place.

Since the pressure conditions with regard to aqueous sludge phases may present a problem in terms of the pressure resistance of the lines, one of the lines L1, L12 or both lines L1, L12 preferably has or have a pressure relief valve (not illustrated here). I n fig. 1, the recirculation of the aqueous phase is taken over by a (sludge) pump P3 which, during operation, preferably works with a lower power, preferably with less than 15% of the power of the bilge water pump P1.

Recirculation may take place continuously or else only intermittently. As a result of the recirculation of the sludge phase, the latter is mixed with the bilge water to be conducted into the centrifuge and is purified together with this bilge water, thus, overall, reducing the water content in the sludge phase, as compared with the system of fig. 2. In this way, the disposable quantity of purified bilge water phase W is increased in a simple way or the volume to be stored per unit of volume of bilge water in the sludge collection tank 10 is reduced.

Preferably, recirculation through the line L12 or the pump P2 is stopped when a program for emptying the centrifuge starts (if the latter has a piston slide emptying function) or when an alarm has been triggered.

The filter 2 may be utilized in order to establish whether the sludge content in the inflow to the centrifuge is too high. In this case, the pump P2 is stopped. A pressure transmitter and vibration monitoring further increase safety, where appropriate.

Preferably, a nonreturn valve (not shown) is connected into the recirculation line L12 downstream of the sludge collection tank 10, in order to prevent a possible backflow of the bilge water into this container. Furthermore, especially advantageously, the bilge water pump P1 is connected into the line L1 downstream of the nonreturn valve and downstream of the issue of the recirculation line L12 into the line L1.

Fig. 3 shows a further preferred development in which the system of fig. 1 is additionally supplemented by a sludge upgrading device (“sludge concentration unit”), here a settling tank (or, in particular, a press) 11 for dewatering the sludge phase S2 expelled from the centrifuge, said sludge upgrading device being connected into the line L9. By means of this device 11, the sludge phase is additionally upgraded, the liquid phase settling out of the sludge preferably statically. The settled liquid phase can be returned through a line L13 into the sludge collection tank 10 which preferably has the recirculation line L12 (of fig. 1). The sludge S3 can then be disposed of separately from the oil-containing phase. Moreover, in this way, the sludge content in the collection tank 10 for the sludge is reduced, this having a positive effect upon returnability through the line L12.

List of Reference Symbols P1, P2 Pu m ps L1, L2, ... Lines 51 solid particles 52 sludge phase 53 sludge 0,W Oil and water phases B Bilge water V1, V2,... Valves 1 Bilge water collection tank 2 Filter system 3 Steam inflow 4 Steam heater 5 Condensate drain 6 Centrifuge 7 Solids trap 8 Checking device 9 Intermediate tank 10 Sludge collection tank 11 Sludge upgrading device

Claims

1. Groundwater purification plants having at least the following characteristics: A) a bottom water tank (1) for bottom water, B) a centrifuge (6) for separating an oil phase (O) and a solid-like sludge phase (S2) from the bottom water which and C) a sludge collection tank (10) for collecting a separated oil phase (O) and the sludge phase (S2), wherein the sludge collection tank (10) acts as a precipitation tank in which the heavier aqueous sludge phase is collected in the lower area of the tank. said oil phase floating on top, characterized in that D) the sludge collection tank (10) has a recirculation line (L12) which opens into a line (L1) arranged between the bottom water tank (1) for the bottom water and the centrifuge (6), wherein the recirculation line (L12) is arranged at the bottom and / or on a wall in the lower third of the sludge collection tank (10) and wherein the recirculation line (L12) is suitable and provided for at least partial return of sludge phase (S2) from the sludge phase tank (10) into the centrifuge (6 ) or i a contact element connected before the centrifuge (6).

Installation according to claim 1, characterized in that a non-return valve is connected in the recirculation line (L12) after the sludge collection tank (10).

Installation according to claim 1 or 2, characterized in that a non-return valve is connected to the bottom water tank in the conduit (L1) into which the recirculation conduit (L12) opens.

Installation according to claim 3, characterized in that a bottom water pump (P1) is connected to the line (L1) after the check valve, which is inserted into the line (L1) into which the recycle line (L12) opens and after the outlet of the recycle line (L12) line (L1).

Installation according to claim 4, characterized in that the effect of the bottom water pump (P1) is greater than the sludge pump (P2) in the recirculation line (L12).

System according to one of the preceding claims, characterized in that the conduit (L1) into which the recirculation conduit (L12) opens is a suction conduit (L1).

System according to one of the preceding claims 5 or 6, characterized in that the power of the sludge pump (P2) during operation in the recirculation line (L12) is less than 25%, preferably less than 15% of the power of the bottom water pump (1).

System according to one of the preceding claims, characterized in that it has a sludge concentrating device (11) connected to a line (L9) through which the sludge phase (S2) ejected from the centrifuge (6) into a solids catch (7) slamfa-setanken.

A method for the combined processing of bottom water and sludge by means of a plant according to one of the preceding claims, with the following steps: a) providing bottom water in a bottom water tank (1), b) diverting the bottom water from the bottom water tank (1) to a centrifuge (6), c) purifying the bottom water during separation of an oil phase (O) and a sludge phase from a water phase (W) in a centrifuge (6), preferably a separator, d) collecting the sludge phase (S2) and the oil phase (O ) in a sludge collection tank (10) which acts as a precipitation tank in which the heavier aqueous sludge phase is collected in the lower area of the tank and in which the oil phase floats on top, and e) at least partially recycles the sludge phase (S2) from the sludge collection tank (10). into the centrifuge (6) or into a system element connected before the centrifuge (6).

Process according to claim 9, characterized in that the oil content of the bottom water before its clearance is less than 25% by volume.

Process according to claim 9 or 10, characterized in that filtration and / or heating of the bottom water takes place during the diversion of the bottom water according to step b).

Method according to any of the preceding claims 9 to 11, characterized in that the recirculation according to step e) is interrupted when a solid discharge of the separator is performed or when an alarm is triggered. Note: an alarm may be: excessive temperature, exchanger vibration limit value exceeded, etc.

Process according to any one of the preceding claims 9 to 12, characterized in that the solids content of the sludge phase (S2) discharged from the centrifuge is further reduced before introduction into the sludge collection tank (10).

Process according to claim 13, characterized in that the reduction in solids content takes place by means of a press or in a precipitation tank (11).